An image forming apparatus according to the prior art has developer accommodating means for accommodating a developer, and a developer carrier for carrying the developer. In an image forming apparatus of this kind, sensing the remaining amount of developer inside the developer accommodating means by utilizing voltage impressed upon the developer carrier is well known in the art.
For example, a voltage is impressed upon the developer carrier and the electrostatic capacitance between the developer carrier and a developer sensing member, such as a plate antenna provided in the container, is detected, thereby sensing the amount of developer within the developer accommodating container.
However, when the amount of developer is sensed according to the prior art described above, the prior art does not sense the amount of developer taking into consideration the electrification conditions of an electrifying member that is for the purpose of electrifying an image carrier.
For example, a change in the frequency of electrification applied to the electrifying member that electrifies the image carrier has an effect upon the electrostatic capacitance in the container. Accordingly, in a case where an electrification condition of the image carrier is changed, the amount of developer cannot be sensed accurately.